This allows now to compute (the average of) a x-dependant bias.

Based now on JSON files in results folder. evaluate_tabular.py has been
renamed into evaluate_metrics. JSON files have also been updated. Need
to check whether correct now for all datasets.

Previously, this was done by looking at the average of the predictions
over the posterior predictive. This was removed, as this didn't make
much sense.

The evaluate_tabular script was simplified to ease the analysis of more
quantities. Several coverage quantities and the bias were added to these
quantities. However, they perform rather poor.

Added EiV training scripts for the three datasets and moreover included
bias evaluation in `evaluate_tabular`. The inclusion of some coverage
measure is still needed.